Description of the Pest
The green peach aphid and the potato aphid are commonly found on lettuce; of the two, green peach aphid is the most important. Green peach aphids are dark green to yellow and have no waxy covering. The tubercles at the base of the antennae grow toward each other. Infestations start on the lower leaves and as aphid numbers grow they move up and over the entire plant.
Potato aphids can be found in both pink and green forms. This aphid is larger than the green peach aphid, and the adult has longer cornicles and cauda. Potato aphid colonies are composed of both adults and offspring closely clustered together, usually on the youngest leaves. The potato aphid may occur alone, or in colonies with green peach aphid.
Damage
Large numbers of aphids can stunt seedlings or transplants and can contaminate heads bound for market. Green peach aphids can vector several viruses that affect lettuce including alfalfa mosaic, beet western yellows, beet yellow stunt, and turnip mosaic.
Management
Biological Control
The same general predators that attack other aphids also prey on green peach aphids. Epidemics of a disease caused by the fungus Entomophthora aphidis may kill portions of the green peach aphid population when their numbers are high and relative humidity is high. Parasites, including Lysiphlebus testaceipes, Aphidius matricariae, and Aphelinus semiflavus, attack this pest. Natural enemies rarely provide adequate control of large numbers of aphids in spring or fall crops.
Organically Acceptable Methods
Use biological control and sprays of azadirachtin, insecticidal soaps, or selected entomopathogenic fungi in an organically certified crop.
Monitoring
Check all areas of the field twice a week, but especially along the edges, which are usually the first area to become infested. Since green peach aphid infestations are clumped, you will need to sample 25 plants per quadrant of a 40- to 80-acre field.
Management Decisions
If high numbers develop on seedlings, apply insecticide as soon as plants appear stressed. On more mature plants, before heading, do not apply insecticide unless numbers exceed 20 aphids per plant. If a significant percentage of plants are infested just prior to heading, apply insecticide to keep aphids from spreading into the center of the head where they are difficult to control. Continue monitoring to see whether another treatment is needed. Some populations of green peach aphid may be resistant to certain insecticides in your area; check with your farm advisor for more information.
| Common name | Amount per acre** | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used. | ||||
| A. | FLUPYRADIFURONE | |||
| (Sivanto Prime) | 10.5–12 fl oz | 12 | 1 (foliar)
|
|
| 21 (soil) | ||||
| MODE-OF-ACTION GROUP NUMBER1: 4D | ||||
| B. | DINOTEFURAN | |||
| (Venom) | 6 oz | 12 | 21 | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| COMMENTS: Apply as a soil application at planting. | ||||
| C. | DIAZINON* | |||
| (various products) | Label rates | 72 | 14 | |
| MODE-OF-ACTION GROUP NUMBER1: 1B | ||||
| COMMENTS: Foliar application. Avoid drift and tailwater runoff into surface waters. | ||||
| D. | IMIDACLOPRID | |||
| (Admire Pro) | 7–10.5 oz | 12 | 21 | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| COMMENTS: Soil application. Placement is critical; see label for information. Do not apply more than 0.38 lb a.i. of Admire Pro/acre per year. | ||||
| E. | AZADIRACHTIN# | |||
| (Aza-Direct 1.2%) | 8.3–40 oz | 4 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: 18B | ||||
| COMMENTS: Restricted use product in an organically certified crop. | ||||
| F. | FLONICAMID | |||
| (Beleaf 50SG) | 2–2.8 oz | 12 | 0 | |
| MODE-OF-ACTION GROUP NUMBER1: 9C | ||||
| G. | SPIROTETRAMAT | |||
| (Movento) | 4–5 fl oz | 24 | 3 | |
| MODE-OF-ACTION GROUP NUMBER1: 23 | ||||
| H. | INSECTICIDAL SOAP# | |||
| (M-Pede) | Label rates | 12 | 0 | |
| MODE OF ACTION: A contact insecticide with smothering and barrier effects. | ||||
| I. | ACETAMIPRID | |||
| (Assail 70WP) | 0.8–1.2 oz | 12 | 7 | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| COMMENTS: Foliar application. Allow 7 days between applications with a maximum of 5 applications per season. | ||||
| J. | PYMETROZINE | |||
| (Fulfill) | 2.75 oz | 12 | 7 | |
| MODE-OF-ACTION GROUP NUMBER1: 9B | ||||
| K. | THIAMETHOXAM | |||
| (Actara) | 1.5–3.0 oz | 12 | 7 | |
| MODE-OF-ACTION GROUP NUMBER1: 4A | ||||
| ** | Mix with enough water to provide complete coverage. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |
| * | Permit required from county agricultural commissioner for purchase or use. |
| # | Acceptable for use on organically grown produce. |
| 1 | Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee). |